ULTRASONIC SPECTROSCOPY OF LIQUIDS - EXTENDING THE FREQUENCY-RANGE OF THE VARIABLE SAMPLE LENGTH PULSE TECHNIQUE

A method is described that allows the ultrasonic absorption coefficient alpha of liquids to be precisely measured between about 1 and 100 MHz. The automatic measuring procedure can be performed easily and comparatively fast. At high alpha values the accuracy of the method is clearly superior to the more time-consuming resonator technique, which is applied in this frequency range. This accuracy is achieved by careful construction and adjustment of the specimen cell, by semi-empirical consideration of diffraction effects within the sample, and by precise calibration of the set-up by a specially designed below cut-off piston attenuator. The short measuring time is enabled by the particular mode of operation also described in this paper.